A liquid parahydrogen target for the measurement of a parity-violating gamma asymmetry in (n)over-right-arrow + p → d plus γ

被引：13

作者：

Santra, S. ^{[1
]}

Palos, L. Barron ^{[2
]}

Blessinger, C. ^{[1
]}

Bowman, J. D. ^{[3
]}

Chupp, T. E. ^{[4
]}

Covrig, S. ^{[5
]}

Crawford, C. ^{[7
]}

Dabaghyan, M. ^{[5
]}

Dadras, J. ^{[6
]}

Dawkins, M. ^{[1
]}

Gericke, M. T. ^{[1
]}

Fox, W. ^{[1
]}

Gillis, R. C. ^{[8
]}

Leuschner, M. B. ^{[1
]}

Lozowski, B. ^{[1
]}

Mahurin, R. ^{[6
]}

Mason, M. ^{[5
]}

Mei, J. ^{[1
]}

Nann, H. ^{[1
]}

Penttila, S. I. ^{[3
]}

Salas-Bacci, A. ^{[3
]}

Sharma, M. ^{[4
]}

Snow, W. M. ^{[1
]}

Wilburn, W. S. ^{[3
]}

机构：

[1] Indiana Univ, Cyclotron Facil, Bloomington, IN 47408 USA

[2] Arizona State Univ, Tempe, AZ 85287 USA

[3] Los Alamos Natl Lab, Los Alamos, NM 87545 USA

[4] Univ Michigan, Ann Arbor, MI 48104 USA

[5] Univ New Hampshire, Dept Phys, Durham, NH 03824 USA

[6] Univ Tennessee, Dept Phys, Knoxville, TN 37996 USA

[7] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA

[8] Univ Manitoba, Dept Phys, Winnipeg, MB R3T 2N2, Canada

来源：

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT | 2010年 / 620卷 / 2-3期

基金：

美国国家科学基金会;

关键词：

Liquid parahydrogen; Parity-violation; gamma-asymmetry; Neutron depolarization; Bubble suppression; Hydrogen safety; Cryorefrigerator; Ortho-to-para converters; HYDROGEN TARGET; CIRCULAR-POLARIZATION; ELECTRON; THIN;

D O I：

10.1016/j.nima.2010.04.135

中图分类号：

TH7 [仪器、仪表];

学科分类号：

0804 ; 080401 ; 081102 ;

摘要：

A 161 liquid parahydrogen target has been developed for a measurement of the parity-violating gamma-asymmetry in the capture of polarized cold neutrons on protons in the (n) over right arrow + p -> d + gamma reaction by the NPDGamma collaboration. The target system was carefully designed to meet the stringent requirements on systematic effects for the experiment and also to satisfy hydrogen safety requirements. The target was designed to preserve the neutron polarization during neutron scattering on liquid hydrogen (LH2), optimize the statistical sensitivity to the (n) over right arrow + p -> d + gamma reaction, minimize backgrounds coming from neutron interaction with the beam windows of the target cryostat, minimize LH2 density fluctuations which can introduce extra noise in the gamma asymmetry signal, and control systematic effects. The target incorporates two mechanical refrigerators, two ortho-para convertors, an aluminum cryostat, an aluminum target vessel shielded with Li-6-rich plastic, a hydrogen fill/vent line with a passive recirculation loop to establish and maintain the equilibrium ortho-para ratio, a hydrogen relief system coupled to a vent stack, a gas handling system, and an alarm and interlock system. Low Z, nonmagnetic materials were used for the target vessel and cryostat. Pressure and temperature sensors monitored the thermodynamic state of the target. Relative neutron transmission measurements were used to monitor the parahydrogen fraction of the target. The target was thoroughly tested and successfully operated during the first phase of the NPDGamma experiment conducted at the FP12 beam line at Los Alamos Neutron Science Center (LANSCE). An upgraded version of the target system will be used in the next stage of the experiment, which will be performed at the Fundamental Neutron Physics Beam (FnPB) line of the Spallation Neutron Source at Oak Ridge National Laboratory. (C) 2010 Elsevier B.V. All rights reserved.

引用

页码：421 / 436

页数：16

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